My 1993 Ford ranger XLT 4.0 is running like it's missing at idle and stumbles at the crack of the throttle. The computer set a code 157 and a hard fault code. Can anybody help me figure out what might be wrong?

 

1993 Ford codes seen here: https://therangerstation.com/tech_li...gitcodes.shtml

157 (R,M) Mass Air Flow signal is/was low or grounded - MAF

On the air filter box you will see the big air tube that runs to the upper intake on the engine
On the air filter end of that tube is the MAF sensor, it has a 4 wire connector
Unplug that connector

Start the engine and see if it runs better

MAF sensor is heated by 12v and ground, thats 2 of the wires
The other two wires are for the sensor
The computer sends the MAF sensor 5volts on one wire, it will get back .5v to 3.5v on the other wire
.5v is low air flow, 3.5v is high air flow, computer uses this voltage to add the correct amount of gasoline to the engine, so wrong voltage = poor running

157 means computer is getting under .5volt, so MAF sensor either needs to be clean, or has failed.........OR one of these 2 wires is shorted to ground

Dirty MAF sensor is one of the most common issues on fuel injected engines
Its very easy to clean with a spray cleaner, must be an electronics cleaner, not like Windex, lol

 

Thanks for the help really appreciate it.